ext4: Use new buffer_head flag to check uninit group bitmaps initialization

For uninit block group, the on-disk bitmap is not initialized. That
implies we cannot depend on the uptodate flag on the bitmap
buffer_head to find bitmap validity.  Use a new buffer_head flag which
would be set after we properly initialize the bitmap.  This also
prevents (re-)initializing the uninit group bitmap every time we call 
ext4_read_block_bitmap().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

4 files changed, 85 insertions, 6 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 1b26b68aa428..6bba06b09dd1 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -320,20 +320,41 @@ ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
                             block_group, bitmap_blk);
                 return NULL;
         }
-        if (buffer_uptodate(bh) &&
-            !(desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)))
+
+        if (bitmap_uptodate(bh))
                 return bh;
 
         lock_buffer(bh);
+        if (bitmap_uptodate(bh)) {
+                unlock_buffer(bh);
+                return bh;
+        }
         spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group));
         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
                 ext4_init_block_bitmap(sb, bh, block_group, desc);
+                set_bitmap_uptodate(bh);
                 set_buffer_uptodate(bh);
                 spin_unlock(sb_bgl_lock(EXT4_SB(sb), block_group));
                 unlock_buffer(bh);
                 return bh;
         }
         spin_unlock(sb_bgl_lock(EXT4_SB(sb), block_group));
+        if (buffer_uptodate(bh)) {
+                /*
+                 * if not uninit if bh is uptodate,
+                 * bitmap is also uptodate
+                 */
+                set_bitmap_uptodate(bh);
+                unlock_buffer(bh);
+                return bh;
+        }
+        /*
+         * submit the buffer_head for read. We can
+         * safely mark the bitmap as uptodate now.
+         * We do it here so the bitmap uptodate bit
+         * get set with buffer lock held.
+         */
+        set_bitmap_uptodate(bh);
         if (bh_submit_read(bh) < 0) {
                 put_bh(bh);
                 ext4_error(sb, __func__,
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ec862f4ca89f..695b45cc34e7 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -19,6 +19,7 @@
 #include <linux/types.h>
 #include <linux/blkdev.h>
 #include <linux/magic.h>
+#include <linux/jbd2.h>
 #include "ext4_i.h"
 
 /*
@@ -1352,6 +1353,23 @@ extern int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode,
 extern int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                         __u64 start, __u64 len);
 
+/*
+ * Add new method to test wether block and inode bitmaps are properly
+ * initialized. With uninit_bg reading the block from disk is not enough
+ * to mark the bitmap uptodate. We need to also zero-out the bitmap
+ */
+#define BH_BITMAP_UPTODATE BH_JBDPrivateStart
+
+static inline int bitmap_uptodate(struct buffer_head *bh)
+{
+        return (buffer_uptodate(bh) &&
+                        test_bit(BH_BITMAP_UPTODATE, &(bh)->b_state));
+}
+static inline void set_bitmap_uptodate(struct buffer_head *bh)
+{
+        set_bit(BH_BITMAP_UPTODATE, &(bh)->b_state);
+}
+
 #endif  /* __KERNEL__ */
 
 #endif  /* _EXT4_H */
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index d4e544f30be2..7b12aedc5319 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -115,20 +115,40 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
                             block_group, bitmap_blk);
                 return NULL;
         }
-        if (buffer_uptodate(bh) &&
-            !(desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)))
+        if (bitmap_uptodate(bh))
                 return bh;
 
         lock_buffer(bh);
+        if (bitmap_uptodate(bh)) {
+                unlock_buffer(bh);
+                return bh;
+        }
         spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group));
         if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
                 ext4_init_inode_bitmap(sb, bh, block_group, desc);
+                set_bitmap_uptodate(bh);
                 set_buffer_uptodate(bh);
                 spin_unlock(sb_bgl_lock(EXT4_SB(sb), block_group));
                 unlock_buffer(bh);
                 return bh;
         }
         spin_unlock(sb_bgl_lock(EXT4_SB(sb), block_group));
+        if (buffer_uptodate(bh)) {
+                /*
+                 * if not uninit if bh is uptodate,
+                 * bitmap is also uptodate
+                 */
+                set_bitmap_uptodate(bh);
+                unlock_buffer(bh);
+                return bh;
+        }
+        /*
+         * submit the buffer_head for read. We can
+         * safely mark the bitmap as uptodate now.
+         * We do it here so the bitmap uptodate bit
+         * get set with buffer lock held.
+         */
+        set_bitmap_uptodate(bh);
         if (bh_submit_read(bh) < 0) {
                 put_bh(bh);
                 ext4_error(sb, __func__,
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index aac33590ac64..18a52d39d094 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -794,22 +794,42 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
                 if (bh[i] == NULL)
                         goto out;
 
-                if (buffer_uptodate(bh[i]) &&
-                    !(desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)))
+                if (bitmap_uptodate(bh[i]))
                         continue;
 
                 lock_buffer(bh[i]);
+                if (bitmap_uptodate(bh[i])) {
+                        unlock_buffer(bh[i]);
+                        continue;
+                }
                 spin_lock(sb_bgl_lock(EXT4_SB(sb), first_group + i));
                 if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
                         ext4_init_block_bitmap(sb, bh[i],
                                                 first_group + i, desc);
+                        set_bitmap_uptodate(bh[i]);
                         set_buffer_uptodate(bh[i]);
                         spin_unlock(sb_bgl_lock(EXT4_SB(sb), first_group + i));
                         unlock_buffer(bh[i]);
                         continue;
                 }
                 spin_unlock(sb_bgl_lock(EXT4_SB(sb), first_group + i));
+                if (buffer_uptodate(bh[i])) {
+                        /*
+                         * if not uninit if bh is uptodate,
+                         * bitmap is also uptodate
+                         */
+                        set_bitmap_uptodate(bh[i]);
+                        unlock_buffer(bh[i]);
+                        continue;
+                }
                 get_bh(bh[i]);
+                /*
+                 * submit the buffer_head for read. We can
+                 * safely mark the bitmap as uptodate now.
+                 * We do it here so the bitmap uptodate bit
+                 * get set with buffer lock held.
+                 */
+                set_bitmap_uptodate(bh[i]);
                 bh[i]->b_end_io = end_buffer_read_sync;
                 submit_bh(READ, bh[i]);
                 mb_debug("read bitmap for group %u\n", first_group + i);